1. Field of the Invention
The present invention relates to apparatus and to a method for conducting assays and, in particular, to multi-well plate structures for receiving and holding, in separate wells, volumes of liquid for the purpose of conducting chemical or biochemical assays. Multi-well trays or plates having a 2-dimensional array of small wells are commonly used in medicine and science to facilitate testing of a liquid analyte. One particular area of use is blood screening where blood or blood products are introduced into the wells to test for viruses such as HIV, heptitis etc.
2. Description of the Related Art
Such tests (immunoassays) typically involve an antigen-antibody interaction, where the surfaces of the wells are coated with specific antigen itself. This approach detects circulating antibodies to that specific antigen. Alternatively the wells can be coated with a specific antibody which captures circulating antigen which is, in turn, identified by a second antibody directed against a second epitope on the captured antigen. These two approaches are just two of the large number of variants developed in immunoassay (review Principles and Practice of Immunoassay Price & Newman 1997 ISBN 1-56159-145-0).
In an immunoassays sample must be applied and in most cases subsequent addition of reagents or washing buffer is required. Typically the well is exposed to blood or blood product and the well is rinsed clean and a further reactant, which binds either to exposed antibodies or captured antigens is introduced into the wells, to create an observable reaction. These reactions may produce a colour or some other observable change. This enables the wells containing specific antigen antibody reactions to be identified and the extent of these reactions quantified.
It is often necessary to fill each well of a multi-well tray with a precisely defined volume of analyte. This is normally achieved using a single or multi-headed micro-pipette. However, this process is often time consuming and, particularly where a large number of wells are to be filled can lead to a number of wells being missed.